Segmented ferrite sonar transducer with permanent magnet bias



' y 1958 D. LEIBOWITZ ET AL 3,382,569

SEGMENTED FERRITE SONAR TRANSDUCER WITH PERMANENT MAGNET BIAS Original Filed Sept. 3, 1963 FIG. I

m m m2 m m D M N w ALFRED SOMMER United States Patent Office 3,382,569 Patented May 14, 1968 ABSTRACT OF THE DISCLOSURE A method of making a transducer ring. A plurality of arcuate ferrite segments are formed and the ends thereof are ground to provide a fiat surface for intimate contact with the ends of adjacent segments. Recesses are drilled into each end of the segments and permanent magnets are inserted into the recesses so that when the segments are placed in abutting contact with one another to form a complete ring, each magnet is positioned with one received in one segment and its other end received in an adjacent segment. The assembled ring is wrapped with a binding material and then with an electrically conductive winding.

The present invention relates to sonar transducers and more particularly to segmented sonar transducers having a permanent magnet bias.

This application is a division of copending application Ser. No. 306,392, filed Sept. 3, 1963, now Patent No. 3, 296,584.

In the practical application of transducers, polarization has previously been produced by electromagnetic means. With such a polarization, the field coils used were bulky which in itself, made the device bulky and difficult to handle. While permanent magnets have been used to eliminate the limitations of the electromagnetic means, the units themselves are still large and bulky since the arrangement and placement of the magnets in the device are generally inside of the transducer housing and in order to accommodate a proper magnet arrangement, the housing itself must be made large and bulky.

This invention relates to a magnetostrictive electroacoustic transducer in which the polarizing field is estab lished by mounting permanent magnets inside of ferrite rings thereby making the device lighter, easier to handle and eliminates the need for water proofing.

An object of the present invention is the provision of providing a omni direction segmented toroidal ferrite sonar transducer having a high coupling coefiicient and high elficiency.

Another object is to provide a segmented ring ferrite transducer having permanent magnet inserts.

A further object of the invention is the provision of ferrite transducer which requires no additional direct current power supply.

A further object of the present invention is the provision of a method of forming a transducer ring from segmented members.

A final object of the present invention is the provision of a transducer made entirely of ferrite rings thereby eliminating the corrosive effects of water.

Other objects and advantages of the invention will hereinafter become more fully apparent from the following description of the annexed drawings, which illustrate a preferred embodiment and wherein:

FIG. 1 is an isometric view of one complete segmented ferrite ring showing a broken away section at the magnet insert area.

FIG. 2 is an isometric view of the segmented ferrite ring shown in FIG. 1, having representative windings.

FIG. 3 is an isometric view of one segment of the cemented ferrite ring shown in FIGS. 1 and 2.

FIG. 4 is an isometric view showing several segmented ferrite rings forming the preferred transducer.

Briefly, the invention entails placing permanent magnets, which act as a DC. bias source, in segments of a ferrite ring forming a transducer thereby eliminating the requirement of an additional D.C. source.

Referring now to the drawings in detail, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIG. 1 a. transducer ring 10 which is formed from a number of segments or blocks 12 as shown in FIG. 3.

Initially blocks 12, which are formed from an N-51 ferrite material, are fitted with magnets 14 which are grain oriented so as to give the maximum field strength and coercive force. Each block 12 is accurately machined with the ends being ground at an angle accurate to five minutes of are, so that upon assembly an accurate ring 10 is formed. After the magnets 14 are assembled in blocks 12, the blocks and magnets are magnetized in the pole piece$ of a large electromagnet. The blocks having the magnets therein are now assembled into a ring 10, with the magnets 14 fitting into holes 16 of an adjacent block until the complete arcuate ring is formed. A cement such as Epon V or araldite, placed on Teflon or drafting cloth, is used to cement the blocks together, however any type of cement material which can readily be used with N-51 ferrite can be used. The completed ring is now cured for the proper curing cycle of the adhesive used.

FIG. 2 shows the assembled ring 10, having A.C. windings 18. Though these windings are shown as raised above the ring surface, for clarification purposes, they are generally wound adjacent the ring surface.

FIG. 4 shows ring 10 mounted on a drum 20, with the drum having a A.C. power connection 22 mounted thereon. Drum 22 may be of any material, but is preferably made of metal. Aperture 24 is used as a means of raising and lowering the transducer in and out of water, and cable 26 is a transmission line for the A.C. power supply from the water surface when the device is in use. Though only three rings are shown mounted on drum 20, during operation the rings 10 would completely cover the face of drum 20, with the windings of each individual ring connected to the A.C. power supply 22.

In operation, an A.C. power supply operating at approximately 2800 c.p.s. and approximately one wave length long is supplied to each ring 10, by cable 26 through connector 22. Since there is a constant D.C. source applied on the rings at alltimes by the permanent magnet inserts the material is said to be polarized. Upon applying an A.C. power source to the rings, the rings will contract in and out as is expected of a transducer, and therefor supply acoustic motion to the water. It can readily be seen, that the magnets add to the alternating current and thereby contract and expand the field. As has been described, the device needs no additional A.C. source, since it is always D.C. biased, is -88% efficient, and may be submerged without additional protection for the housmg.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood, that with the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. The method of making a transducer ring the steps comprising:

forming a plurality of arcuate ferrite segments, grinding said segments at the ends to provide fiat end surfaces which lie within planes which intersect at the axis of said arcuate segments,

drilling said segments at both of said ground ends thereby forming apertures,

placing magnets in the apertures formed at one end,

assembling said arcuate segments into a ring with each of said magnets being positioned with one end thereof received in one segment and the opposite end thereof received in an adjacent segment,

wrapping said ring with a binding material,

curing said ring, and

wrapping said ring with electrically conductive windings.

2. The method according to claim 1 wherein the angles ground on said arcuate segments have a tolerance of five minutes of arc.

References Cited UNITED STATES PATENTS Albers-Schoenberg 29-608 X CHARLIE T. MOON, Primary Examiner.

D. C. REILEY, Assistant Examiner. 

